1. Field of the Invention
This invention relates to a program, a medium, a method for selecting a disc, and an optical disc apparatus. More specifically, this invention relates to a program used by an apparatus which works with plural types of optical discs, and a medium on which the program is recorded. This invention also relates to a method for selecting a type of optical disc and a preferred optical disc apparatus for carrying out the method.
2. Description of the Related Art
A personal computer, with certain upgraded functions, can be used to process audio-visual (AV) information, such as sound or video information. Because of the very large volume of such AV information, optical discs like compact disc (CD) and digital versatile disc (DVD) are being considered as information recording media. Thus, apparatuses for accessing optical discs are widely used as peripheral equipment due to low cost.
The types of optical discs available have increased as types of information brought up various topics. For example, there are CD-ROM, CD−R (CD−recordable), and CD−RW (CD−rewritable), etc., as optical discs of CD origins. There are also DVD-ROM, DVD-RAM, DVD−R (DVD−recordable), DVD−RW (DVD−rewritable), DVD+R (DVD+recordable), and DVD+RW (DVD+rewritable), etc., as optical discs of DVD origins.
Optical disc apparatuses that can access (i.e., that work with) both CD and DVD (so-called combination drive) have come onto the market for use with downsized personal computers. The combination drive sets up its operating conditions corresponding to the type of optical disc to be accessed. For example, the drive selects a light source that emits a beam of light with a wavelength of 780 nm for the optical disc of CD origin. On the other hand, the drive selects a light source that emits a beam of light with a wavelength of 650 nm for the optical disc of DVD origin. The recording surfaces of CD−R and CD−RW drives have different reflectivities. Consequently, to accommodate the different reflectivities, the optical disc apparatus sets different gains for adjusting levels regarding output signals from a photo acceptance unit in an optical pick up device.
Write at once optical discs, such as CD−R and DVD+R, which have organic dye in a recording layer, and rewritable optical discs, such as DVD+RW, CD−R and DVD+R, which have a special alloy, have different recording modes. Accordingly, the optical disc apparatus has to change the power of the laser beam emitted by the light source during the formation of marks (pits), i.e. during the controlling of write power, corresponding to the type of optical disc. It is necessary for optical disc drives to determine the type of optical disc to be accessed for accessing precisely.
There is a method for detecting a focus position as a method for judging whether an inserted disc is CD or DVD. An optical disc apparatus assumes an optical disc to be DVD and sets various conditions for DVD. The optical disc apparatus then drives a focus servo for an inserted optical disc and, as an example, compares a level of a focus error signal with a predetermined threshold level. The optical disc apparatus checks whether the focus position can be detected normally or not based on a result of the comparison. If the focus position can be detected normally, the optical disc apparatus judges that the inserted optical disc is a DVD.
If the focus position cannot be detected normally, the optical disc apparatus judges that the inserted optical disc is not a DVD and assumes the disc to be a CD and sets various conditions for CD. If the focus position can be detected normally, the optical disc apparatus judges that the inserted optical disc is a CD. If the focus position cannot be detected normally, the optical disc apparatus executes predetermined error processes. Since the optical disc apparatus has to select a type of optical disc after assuming a type of optical disc in order of preset and setting various conditions for the assumed optical disc in the above-mentioned disc selecting method, it may take a long time to make a selection if there are many types of optical discs that can be selected.
Japanese Laid-open patent application 2000-149,392 discloses a disc reproducing apparatus which pumps and dumps an objective lens in a vertical direction relative to a signal recording surface on a disc when the disc is mounted. The disc reproducing apparatus selects a type of optical disc (DVD with monolayer, DVD with double layer, CD-ROM and CD−RW) based on the number of S curves and amplitude value included in detected focus error signals. This disc reproducing apparatus, however, has to limit the types of discs that can be selected because of selecting based on the S curve included in the focus error signal.
An object of the present invention is to provide a program product and a medium on which the program is recorded. The program is executed by a control computer in an optical disc apparatus. The apparatus can access plural types of optical discs. The control computer is able to select a type of set optical disc. Another object of the present invention is to provide a method for selecting a type of disc. It can take a short time to select a type of optical disc by this method. Another object of the present invention is to provide an optical disc apparatus which can handle plural types of optical discs, and which determines the type of the set optical disc in a short period of time.